1. Field of the Invention
This invention relates generally to mirrors and more particularly to an apparatus for ensuring correct coverage of a critical field of view in automobile rear-view and side-view mirrors.
2. Description of the Background Art
Having an unobstructed field of view is essential for drivers of motor vehicles, and for this reason automobiles and trucks are equipped with a number of mirrors. Typically, a rectangular mirror is mounted inside the center of the windshield to provide a view to the rear of the vehicle. Mirrors are also mounted on each side of vehicles for additional perspectives.
It is often difficult for a driver to judge whether the rear-view mirrors are properly adjusted to provide an adequate view. If a driver needs to adjust a mirror while moving along a curved road, the changing orientation of the car relative to the road behind the vehicle makes it difficult for the driver to aim the mirror correctly. Even when the vehicle is on a straight road, many drivers do not know how to adjust the mirror. Moving or stationary vehicles that must be seen by the driver of the car for safety reasons may not be visible to the driver when looking through the mirror. The field of view that determines the safe zone is termed as the critical field of view. An improperly adjusted mirror may leave the viewer a xe2x80x9cblind spotxe2x80x9d in which the viewer cannot see the entire critical field of view.
The uncertainty in mirror adjustment is due to several factors. Firstly, there is no easily identifiable target against which to adjust the mirror. In a dynamic environment, any selected reference object is in motion relative to the vehicle. Secondly, the seated position of the person who adjusts the mirror may be different from the position of the person who uses the adjusted mirror. Finally, the field of view changes with changes in the seated position of the viewer.
Current mirror adjustment methods presume the viewer is in a simple and stable environment and make little or no provision for a real and dynamic environment. Therefore, there is a need for an apparatus that will assist individuals and machines to correctly adjust a mirror to ensure the correct coverage of the critical field of view.
The present invention ensures correct coverage of a critical field of view by providing a mirror or other optical assembly with reference points that a viewer can utilize to correctly adjust the direction of the mirror. The invention places at least two reference points such that when they appear to a user to be in their designated positions with respect to one another, the optical device is properly aligned. Typically, their designated positions are where one reference mark appears to be directly behind the other, along the user""s line of sight. The reference points could be markings, light sources, or translucent, opaque or reflective objects, for example. The reference points may also be the image of two or more objects such as markings rather than the objects themselves.
In one embodiment, the reference points are dots located on the center of a mirror and on a fixed inner glass and a fixed outer glass located immediately in front of the mirror. Aligning the dot on the mirror until it is directly behind the dots on the inner and outer glass (or coincident with images of the inner and outer glass dots in the mirror), obtains the correct coverage of the critical field of view.
In an alternative embodiment, a light source produces the reference points. The light is reflected by a back surface of the mirror coated with material in a concentric gradient pattern. The resulting reflection is a reflected spot corresponding to the center of the pattern and a shaded area corresponding to the concentric portion of the pattern. A viewer looking along a line of sight sees the shaded area. When the mirror is tilted such that the reflected spot overlaps the shaded area, the mirror is properly adjusted.
In another embodiment, the reference points are two translucent bodies arranged along a line parallel to a line that determines the preferred orientation of the mirror. The image of the two translucent bodies is reflected so that when they both appear to be aligned with the user""s line of sight the mirror is properly aligned. Preferably, the two translucent bodies are illuminated using a light placed behind or in front of them.